1. Technical Field
The present invention relates to a liquid ejecting head unit used in a liquid ejecting apparatus, such as an ink jet recording apparatus, and it also relates to a liquid ejecting apparatus and a method of producing the liquid ejecting apparatus. In particular, the invention relates to a liquid ejecting head unit, a liquid ejecting apparatus, and a method of producing the liquid ejecting apparatus in which a plurality of liquid ejecting heads are attached to a head fixing member in a removable manner.
2. Related Art
Liquid ejecting apparatuses include liquid ejecting heads that eject droplets of liquid. Various types of liquid can be ejected from the liquid ejecting heads. A typical example of the liquid ejecting apparatus is an image recording apparatus, such as an ink jet recording apparatus (printer) that has an ink jet recording head (a “recording head”) and performs recording by ejecting droplets of liquid ink from nozzles in the recording head. In recent years, the application of the liquid ejecting apparatus is not limited to the image recording apparatus, but it can be applied to various types of manufacturing apparatuses, such as display manufacturing apparatuses. In image recording apparatuses, recording heads eject liquid ink, and in display manufacturing apparatuses, colorant ejecting heads eject red (R), green (G), and blue (B) colorant solutions. In addition, in electrode-producing apparatuses, electrode-material ejecting heads eject a liquid electrode material, and in chip manufacturing apparatuses, living-organic-material ejecting heads eject a living-organic-material solution.
In recent years, some printers employ a multi-head configuration, in which a single head unit includes a plurality of recording heads, each having nozzle rows consisting of several rows of nozzles, arranged side-by-side and fixed to a head fixing member, such as a sub-carriage. In a configuration in which the recording heads are positioned and screwed to the sub-carriage, the positioned recording heads are temporarily bonded to the sub-carriage with adhesive (for example, an instant adhesive) before screwed. This prevents the recording heads from being displaced by a rotational moment generated when they are securely screwed. If, as in this case, the recording heads are temporarily bonded to the sub-carriage with adhesive, it is difficult to remove the recording heads from the sub-carriage for repair or replacement. To overcome this problem, JP-A-2007-90327 proposes a configuration in which intermediate members called spacers are disposed between the sub-carriage and the recording heads. In that configuration, spacers are screwed to the recording heads in advance. The spacers are then temporarily bonded to the sub-carriage with adhesive and then securely screwed to the sub-carriage. By loosening the screws that fasten the spacers to the recording heads, the recording heads fixed to the sub-carriage can be removed from the spacers and the sub-carriage. Thus, the recording heads can be easily attached and removed for replacement or repair.
When the spacers are temporarily bonded to the sub-carriage with adhesive, the amount of injected adhesive may vary. In a head unit that is reduced in size by reducing the distance between adjacent liquid ejecting heads, an insufficient amount of adhesive may decrease the bonding strength between the sub-carriage and the spacers, deteriorating the positional accuracy of the liquid ejecting heads. In particular, if the positions of the nozzles in the head unit are shifted from each other, liquid ejected from the nozzles may miss the intended landing position on a recording medium. This may degrade the quality of an image recorded on the recording medium.
However, if the amount of adhesive is too large, the excess adhesive may flow out of a bonding surface (a mounting position) of the liquid ejecting head and cure at an unwanted position. For example, the adhesive may flow into the bonding surfaces of the adjacent liquid ejecting heads and cure before the liquid ejecting heads to be bonded to these bonding surfaces are bonded. Unevenness resulting from the adhesive deposited on the bonding surfaces of the adjacent liquid ejecting heads sometimes deteriorates the positional accuracy of the liquid ejecting heads bonded to these bonding surfaces.
This problem is not specific to the ink jet recording apparatus having recording heads for ejecting ink but is present in other liquid ejecting head units in which liquid ejecting heads are fixed to a head fixing member, such as the above-mentioned sub-carriage, with intermediate members, such as spacers, therebetween, and in liquid ejecting apparatuses having such liquid ejecting head units.